Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;

long h,w,white;
vector<bool> is_white;
vector<long> aaa;

void dfs(long a,long b) {
  aaa[a]=b;
  if(a+w<h*w) if(is_white[a+w]&&b+1<aaa[a+w]) dfs(a+w,b+1);
  if(a-w>=0) if(is_white[a-w]&&b+1<aaa[a-w]) dfs(a-w,b+1);
  if(a%w!=w-1) if(is_white[a+1]&&b+1<aaa[a+1]) dfs(a+1,b+1);
  if(a%w!=0) if(is_white[a-1]&&b+1<aaa[a-1]) dfs(a-1,b+1);
  return;
}

int main() {
  white=0;
  cin >> h >> w;
  for(int i=0;i<h;i++) {
    string s;
    cin >> s;
    for(int j=0;j<w;j++) {
      is_white.push_back(s[j]=='.');
      if(s[j]=='.') white++;
      aaa.push_back(99999);
    }
  }
  dfs(0,1);
  if(aaa[h*w-1]<99999) cout << white-aaa[h*w-1] << endl;
  else cout << -1 << endl;
}